1. Field of the Invention
This invention relates to a method of controlling the operation of applying a succession of discrete coupling elements one at a time onto a stringer tape in the manufacture of slide fasteners.
2. Prior Art
Various methods and means have been devised for controlling the operation of applying an array of discretely formed coupling elements one at a time onto a stringer tape which is intermittently moved. One such typical method relies on the use of a number of usually about three to four photoelectric detectors provided along the length of a feed chute, wherein an uppermost detector is preset to determine a normal operating speed; a plurality of intermediate detectors are set to reduce the operating speed stepwise or progressively; and a lowermost detector is preset to discontinue the application of coupling elements to the stringer tape. This prior art method has a drawback in that when the operating speed of applying coupling elements to the tape is changed from high to low or vice versa, the apparatus including means of moving the stringer tape and means of applying the coupling elements to the tape would lag behind due to inertia in responding to such speed variations, resulting in irregularities in the inter-spacing between adjacent coupling elements mounted on the tape. Another drawback is that the inventory or amount of coupling elements present in the feed chute is made known only at the areas at which the detectors are installed, but not elsewhere in the chute so that there would inevitably develop certain time loss in the production of slide fasteners as a whole.